Neuropeptide secretion from dense-core vesicles (DCVs) controls many brain functions. Several components of the DCV exocytosis machinery have recently been identified, but the participation of a SEC1/MUNC18 (SM) protein has remained elusive. Here, we tested the ability of the three exocytic SM proteins expressed in the mammalian brain, MUNC18-1/2/3, to support neuropeptide secretion. We quantified DCV exocytosis at a single vesicle resolution on action potential (AP) train-stimulation in mouse CNS neurons (of unknown sex) using pHluorin-tagged and/or mCherry-tagged neuropeptide Y (NPY) or brain-derived neurotrophic factor (BDNF). Conditional inactivation of Munc18-1 abolished all DCV exocytosis. Expression of MUNC18-1, but not MUNC18-2 or MUNC18-3, supported DCV exocytosis in Munc18-1 null neurons. Heterozygous (HZ) inactivation of Munc18-1, as a model for reduced MUNC18-1 expression, impaired DCV exocytosis, especially during the initial phase of train-stimulation, when the release was maximal. These data show that neurons critically and selectively depend on MUNC18-1 for neuropeptide secretion. Impaired neuropeptide secretion may explain aspects of the behavioral and neurodevelopmental phenotypes that were observed in Munc18-1 HZ mice.
Bibliographical noteFunding Information:
This work was supported by the ERC Advanced Grant 322966 of the European Union (to M.V.). We thank RobbertZalm for cloning and producing viral particles, Lisa Laan and Desiree Schut for producing glia island cultures and providing primary culture assistance, Joke Wortel for organizing the animal breeding, Joost Hoetjes for genotyping, JurjenBroeke for technical support, Ingrid Saarloos for Western blottings, and members of the Center for Neurogenomics and Cognitive Research DCV team for discussions and helpful input. The authors declare no competing financial interests.
Copyright © 2021 the authors.
Copyright 2021 Elsevier B.V., All rights reserved.
- Dense-core vesicle